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A histotoxin produced by Salmonella
Julia M Lodge1, Alex J Bolton1, Gill D Martin1
1Microbial Molecular Genetics and Cell Biology Group, School of Biological Sciences.
Abstract:
Salmonella Typhimurium strain GM3, known to be histotoxic for explants of terminal rabbit ileum in vitro, produces similar lesions in vitro when sterile filtrates, obtained from live organisms after interaction with gut explants in vitro, are used and when rabbit ligated ileal loops are challenged with live organisms. Epithelial damage occurs rapidly, within 2 h of adding organisms or sterile filtrates. This evidence is construed in terms of a secreted salmonella histotoxin that causes epithelial damage, detaching enterocytes which rapidly degenerate into spheroid cells devoid of microvilli. Typhimurium strain GM3 invades ileal mucosa and bacteria are found in the subepithelial tissues. After 12 h, bacteria were seen to be expelled from infected villi in a manner similar to that seen in non-histotoxic infection with Typhimurium strain TML.
Insights
Salmonella Typhimurium strain GM3 causes rapid epithelial damage in rabbit ileum by secreting a histotoxin. This toxin detaches enterocytes, leading to degeneration and invasion, but bacteria are eventually expelled.
Area of Science:
- Microbiology
- Pathology
- Gastroenterology
Background:
- Salmonella Typhimurium is a significant bacterial pathogen.
- Certain strains exhibit histotoxic properties affecting the gut.
- Understanding the mechanisms of Salmonella-induced gut damage is crucial for developing treatments.
Purpose of the Study:
- To investigate the histotoxic effects of Salmonella Typhimurium strain GM3 on rabbit ileum.
- To identify the causative agent of the observed epithelial damage.
- To characterize the interaction between the bacteria and the intestinal mucosa.
Main Methods:
- In vitro studies using rabbit ileal explants.
- Challenge with live Salmonella Typhimurium strain GM3 and its sterile filtrates.
- Analysis of ligated rabbit ileal loops.
- Microscopic examination of epithelial damage and bacterial invasion.
Main Results:
- Salmonella Typhimurium strain GM3 induced rapid epithelial damage within 2 hours.
- Both live bacteria and sterile filtrates caused similar lesions, indicating a secreted toxin.
- Enterocytes detached and degenerated, losing microvilli.
- Bacterial invasion of the ileal mucosa and subepithelial tissues was observed.
- Bacteria were expelled from villi after 12 hours, similar to non-histotoxic strains.
Conclusions:
- Salmonella Typhimurium strain GM3 secretes a histotoxin responsible for rapid epithelial damage in the rabbit ileum.
- The observed pathology involves enterocyte detachment, degeneration, and bacterial invasion.
- The expulsion of bacteria suggests a host defense mechanism against the infection.